This invention relates to balancing systems for making repetitive balance corrections on rotary elements of machines that undergo variations of balance during normal operation and where an imbalance is corrected by remote control while such elements are rotating. More particularly the present invention relates to improvements in the control of such balancing systems.
The above identified two patent applications disclose a new and improved unbalance compensator which is unencumbered by limitations of prior unbalance compensators. The new and improved unbalanced compensator comprises a plurality of balancing chambers arranged circumferentially around the body of the compensator in a symmetrical fashion. Balancing mass is transferred between opposite chambers by creating a temperature differential between fluids contained in the respective chambers. The temperature differential gives rise to a higher vapor pressure in a warmer chamber creating vapor flow through a transfer tube to an opposite cooler chamber where the transferred vapor condenses. The port ends of each transfer tube are located in their respective chambers in such a manner as to prevent liquid fluid from entering and passing through the tube into an opposite chamber whether the compensator is rotating or stopped at any particular angular position. Thus the liquid fluid is essentially restricted to the chambers while only vapor is allowed to move between chambers. The creation of a temperature difference between fluids in opposing chambers may be by either a heating means, a cooling means, or a combination of both.
The above identified two patent applications disclose various types of controls for controlling the heating and cooling chambers for the purpose of performing balance corrections. One form of control employs a heating coil for each chamber. The heating coils are selectively energized. One mode of selective energization is by transmitting power to a selected heating coil through a corresponding slip ring and brush, each heating coil being connected to a corresponding slip ring and brush. In another form of control the slip rings and brushes are replaced by stationary and rotating coils (power and signal coil pair) which are coupled via transformer coupling. Electrical power is transmitted across an air gap via power coils and the appropriate heating coil is selected by means of a signal coupled across the air gap between signal coils. Appropriate electronics are used to encode the signal for transmission and to decode the signal at reception so that the correct heating coil is energized for correcting imbalance. Vibration indicative of imbalance is monitored by a vibration pick-up provided as input information to the electronic control. Phase information as to the angular position of imbalance is also provided as an input to the electronic control by means of a shaft position encoder. The electronic control acts upon this input data to energize the appropriate heating element for creating the required balance mass transfer to correct the imbalance.
The present invention is directed to a new and improved arrangement for the control of an unbalance compensator. One advantage of the present invention is that the electronic control circuitry does not have to be mounted on the rotating mass yet the transmission of electrical power to the heating coils can be accomplished via transformer type action. By removing any electronics from the rotating mass a number of advantages accrue. One advantage is that the separate packaging of the electronics in a module unique to the rotating balance mass can be eliminated. This saves on manufacturing complexities and service considerations. Another advantage is that the electronics can be removed from potential exposure to elevated temperatures. A certain amount of temperature rise may be due to the heat generated by the heating coils for the chambers. If the ambient temperature is also extremely high, the combined effect could give rise to the possibility of spurious operation and/or malfunction of the electronics due its thermal sensitivity. While a package may be designed with insulation and safeguards to protect it against this possibility, removal of the electronics from the rotating mass provides a very desirable alternative in many instances.
A further feature of the invention is that the compensator may be made more compact. Hence it can be used in applications where it might otherwise be impossible or, where extensive modification or rework would be required to a machine to be balanced. Furthermore, manufacturing and assembly considerations for the unbalance compensator are simplified.
In one embodiment the unbalance compensator of the present invention may comprise individual primary and secondary coils for each chamber heating coil. In one species of this embodiment the primary coils may be of a uniform diameter and arranged axially adjacent each other. The secondary coils are of a uniform diameter slightly larger than that of the primary coils and are also disposed axially adjacent each other with each being in axial alignment with the corresponding primary coil. The invention allows the appropriate heating coil to be energized with efficiency and without any significant loss occurring due to leakage to other coils.
In another embodiment of the invention the primary and secondary coils may be constructed as sets of concentric rings concentric with the axis of rotation. Each primary coil confronts the corresponding secondary coil. This arrangement is compact in the axial direction allowing the overall axial dimension of the compensator to be reduced. This is important in accommodating the application of the unbalance compensator to certain types of balance mass requirements.
In still another embodiment of the invention power and signal are transmitted as a composite waveform through electromechanical connections at opposite ends of the rotating mass. These electromechanical connections comprise circular ball stud elements at the axis of rotation at the opposite ends of the rotating mass. Each ball stud is seated in a conically tapered seat formed at one end of a bushing which is resiliently biased against the ball stud. One electromechanical connection is to one side of the line voltage and the other is to the opposite side of the line voltage. One ball stud is part of a module which is mounted concentric with the axis of the unbalance compensator and is of a smaller diameter than the overall diameter of the unbalance compensator. This module contains electronic circuitry and solid state relays. The composite waveform applied via the two electromechanical connections is monitored by the electronic circuitry. The electronic circuitry decodes the signal information to select an appropriate solid state relay. The selection of a solid state relay causes the electrical power component of the composite waveform to be applied to the appropriate heating coil. This embodiment eliminates the use of slip rings and brushes, and it does not require the use of transformer coupled coils on the rotating and non-rotating portions.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.